Field of the Invention
The present invention relates to an image projection apparatus (referred to as a “projector” hereinafter), a control method, and a storage medium.
Description of the Related Art
Some projectors guide to a light modulation element, such as a liquid crystal panel, illumination light that contains fluorescent light generated by irradiating excitation light from a laser diode (LD) onto a fluorescent material as a wavelength conversion element, and displays an image by projecting image light modulated by the light modulation element. One representative example of such a projector forms white light by combing blue light from a blue LD with yellow light as fluorescent light generated by irradiating the blue light as excitation light onto a fluorescent body. Many fluorescent bodies have a low fluorescent conversion efficiency in a red wavelength band. Hence, Japanese Patent Laid-Open No. 2016-21014 discloses a projector that includes a red light source, such as a red LD, in addition to a blue LD and a fluorescent body, and supplements the red light.
Since the deterioration speed is different between the blue LD and the red LD, a color balance of the image projected by the projector may be lost for a long time use. Japanese Patent No. 5593703 discloses a method of correcting a color balance when a blue LD deteriorates in a projector using the blue LD and the fluorescent body that generates the yellow fluorescent light. More specifically, this method corrects the color balance by gain-controlling the light modulation element based on the blue light quantity and the red light quantity measured by the light quantity monitor.
Where the blue LD and the fluorescent body emitting the yellow fluorescent light is combined with the red LED for supplementing the red light, it is necessary to distinguish the light quantity of the red light component in the yellow light from the fluorescent body from the red light quantity from the red LD. This is because the tone of the red light component contained in the fluorescent light and the tone of the light from the red LD are different from each other and therefore the color balance cannot be well corrected unless a reduced red light quantity caused by the deterioration of the red LD is accurately measured.